Behavioral analysis of the repetition deficit in conduction aphasia

9 When a focal cerebral lesion selectively imp a i r s a p a r t i c u l a r cognitive process, the opportunity arises to analyze the deficient performance and thus isolate a component of behavior. In conduction aphasia, the patient finds it disproportionately difficult to repeat spoken words.’ Patients typically also have naming difficulty, defective writing, and difficulty in oral rather than silent reading. Auditory comprehens ion is relatively spared, and spontaneous speech output is quite fluent and free from hesitation.* >3 Behaviorally, the repetition deficit has been characterized as due to loss of short-term verbal memory store, long-term memory remaining intact4 in relation t o a presumptive cortical gray matter lesion. But on neuroanatomic grounds, it has been attributed to a white matter lesion of the arcuate fascicle, disconnecting Wernicke’s area in temporal lobe from Broca’s area in frontal lobe and thus making it impossible for the outcome of auditory word analysis t o be communicated t o the facility for expressive ~ p e e c h . ~ 7’ Alternatively, a left temporal lobe lesion makes it necessary for the patient to utilize his right temporal lobe for auditory-verbal analysis, but then he has no way of passing information o n t o Broca’s area o n the left.6 We present a new at tempt a t a behavioral model of the repetition deficit, which bears on the question of whether the causative deficit is